1. Field of the Invention
The present invention relates to a water resistivity sensor, and more particularly to a compact, battery-powered water resistivity sensor, by means of which resistivity of water can be measured and displayed in terms of actual resistivity values.
2. Description of the Prior Art
Prior art arrangements for sensing water resistivity have been encumbered by several disadvantages. Notable among these disadvantages are: (1) inability to keep power applied to the sensor to a minimum, thus making it difficult to meet safety requirements; (2) inability to minimize power consumed by the sensor; (3) failure to measure and display actual resistivity values; (4) difficulty in developing a compact water resistivity sensor; and (5) failure to develop an inexpensive sensor unit.
For example, in certain arrangements, a signaling light is energized to indicate the end point of useful life of water contained in a storage tank. In such an arrangement, a predetermined conductivity of the water is set, and a lamp is kept energized so long as the conductivity of the water remains below a predetermined point. Power wires are provided for bringing standard household current (115 volt A.C.) to the indicator bulb and the probes, the latter being encapsulated in a common housing. Thus, such an arrangement is characterized by most, if not all, of the disadvantages enumerated above.
In another arrangement of the prior art, an end point quality control light circuit is powered by standard household current, and includes a pair of probes isolated from the source of power. However, the subject circuit applies only 12 volts (approximately) to the water being monitored. Nevertheless, the quality of the water is only indicated by an indicator lamp. Thus, whereas this arrangement does attempt to overcome the first disadvantage enumerated above, the other disadvantages still remain.